Antimissile efforts may use directed-beam weapons, in which the future target missile or target location is not of particular interest, as the speed of the beam is so great that the missile motion is irrelevant. In those cases in which antimissile interceptors with explosive warheads are used, the interceptor speed is of the same order as that of the target missile, and the estimated future location of the target missile is of great importance. The estimated future location of the target missile can be determined by the use of radar. A great deal of effort has been put into antimissile interceptor guidance schemes which predict the future location of the target missile, the interceptor missile, or both, so as to attempt to cause the interceptor to get within a given range of the target missile such that the explosive warhead destroys the target missile. These guidance systems require measurements of the target missile so as to determine its current location, and also require estimates of its projected trajectory.
It is known that rocket engine or rocket motor plumes are hot, and radiate energy across the entire electromagnetic spectrum, including the infrared (IR) portion of the spectrum. The radiated energy constitutes a signature which may allow the rocket engine to be identified or characterized. Different missile systems using either liquid or solid propellant display different infrared (IR) signatures at various altitudes, mach numbers, and aspect angles. These IR signatures have been used for many years to warn of Intercontinental Ballistic Missile (ICBM) launches or to characterize tactical threat systems.
Kinetic weapons (KW) are known for use against threat missiles. Such weapons do not use an explosive charge for destroying the threat missile, but rather rely upon the kinetic energy of a moving object impacting on the hard body of the threat missile. Such schemes have been tested and can be effective. Some antimissile weapons use infrared (IR) schemes for terminal guidance, so as to result in the desired impact between the antimissile weapon and the missile to be destroyed. One of the problems associated with the use of infrared guidance of a kinetic weapon against a boosting missile lies in the inability of the kinetic weapon's infrared seeker to accurately determine the location of the hard body of the target missile in the presence of a hot IR plume from the boost engine.
A proposed solution to the problem of inability of the infrared seeker to distinguish between the hard body of the target missile and the hot plume lies in the use of multiple IR sensors, which respond to different portions of the IR signature, and can distinguish between the hard body and the plume. This solution may be effective, but requires that two or more IR seekers with different characteristics be used. Terminal guidance of a kinetic weapon is facilitated when the sensing and the signal processing are performed on-board the kinetic weapon so as to avoid delays associated with ground-based detection and processing, and data transmission delays. On-board IR sensing with different signatures requires that the kinetic weapon carry two or more different IR sensors, which undesirably adds weight, complexity, and cost to the weapon.